Tile Adhesive
Water retention and anti-sag for C1 / C2 / C2TE classified adhesives.
Coming soon
Product category
Hydroxypropyl Methyl Cellulose (HPMC) for Construction
Hydroxypropyl methyl cellulose (HPMC) is a non-ionic cellulose ether, CAS 9004-65-3, that
keeps water in a fresh mortar and controls its rheology. Construction grades are commonly
banded from 300 to 250,000 mPa·s, measured on a 2% aqueous solution at 20 °C. HPMC is
soluble in cold water and insoluble in hot water.
Spec snapshot
Nine fields a procurement team screens on before reading anything else.
| Field | Value | Basis |
|---|---|---|
| Chemical name | Hydroxypropyl methyl cellulose (HPMC); INN and pharmacopoeial name: hypromellose | Chemistry |
| CAS number | 9004-65-3 | CAS registry |
| HS code | 3912.39 — cellulose ethers, in primary forms | Customs heading; final classification confirmed per destination customs |
| Ionic character | Non-ionic | Chemistry |
| Appearance | White to off-white, free-flowing powder | Material class |
| Solubility | Disperses and swells in cold water; insoluble in hot water | Material class |
| Viscosity banding | 300 – 250,000 mPa·s, 2% aqueous solution at 20 °C | Industry common banding — see the note below |
| Moisture content | Typically ≤ 5–6%, grade-dependent | Industry typical window; the value for a specific grade is stated on its TDS |
| pH, 1% solution | Typically 5–8 | Industry typical window; the value for a specific grade is stated on its TDS |
Two of the rows above describe the material class, not a product specification. Viscosity is quoted at a stated concentration and temperature because the number is meaningless without them, and moisture and pH narrow down by grade. Grade-specific values are only valid when read from the TDS of that grade.
Mechanism
What HPMC does in a mortar
Four functions, each described by mechanism first and site effect second — no adjectives.
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It holds water against suction
Dry substrates, warm aggregate and cement all pull water out of a fresh mix. HPMC adsorbs on the binder and aggregate surfaces and raises the viscosity of the pore solution, so less water migrates into the substrate before the binder has set.
Construction mortars are commonly formulated to land in the 88–95% water-retention window; below roughly 85% the mix stiffens early and adhesion drops, and the exact target depends on how absorbent the substrate is.
88–95% water retention — filter paper / EN 1015-8
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It sets the yield stress, which is what stops sagging
Viscosity band, not dosage alone, governs how the mix behaves on a vertical face: a low band flows and self-levels, a high band holds a bead of adhesive on a wall without slumping.
Anti-sag is a measured property, not an impression — EN 1308 is the reference method for tile adhesives.
T classification in EN 12004: slip ≤ 0.5 mm
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It extends open time
The same adsorbed layer slows evaporative and suction-driven water loss at the surface, which keeps the adhesive able to wet a tile after trowelling.
Open time is highly sensitive to ambient temperature, wind and substrate suction, so a formulation that passes at 20 °C can fail on a hot site.
EN 1346: ≥ 20 min, ≥ 30 min for E-classified products
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It carries the film that holds the mix together
In a hardened mortar the cellulose ether remains as a thin continuous film around binder particles and at the aggregate interface, and that film contributes cohesion.
The same film improves how a redispersible polymer powder distributes through the mix — which is why the two are almost always used together rather than as alternatives.
Paired with RDP, not substituted for it
One side effect worth designing around: HPMC stabilises air bubbles, and the effect grows with dosage and viscosity. Above roughly 0.6% of binder in a cement system, entrained air can cut compressive strength by a visible margin, and a powder defoamer is usually added rather than accepting the loss.
Selection
How to choose a viscosity grade
Viscosity is not a quality ranking: a higher number does not mean a better product. It is a design parameter that has to match substrate suction, coat thickness, application method and the other additives in the formula.
| Band | Viscosity, 2% at 20 °C (mPa·s) | Where it usually fits | What it buys you | What it costs you |
|---|---|---|---|---|
| Low | 300 – 20,000 mPa·s | Self-levelling compounds, gypsum plaster, water-based paint, texture coatings | Flow, high solids, easy air release | Little anti-sag; needs another thickener on vertical work |
| Medium | 20,000 – 60,000 mPa·s | Tile adhesive C1/C2, wall putty, masonry and rendering mortar | Balanced retention and workability; the usual default | Requires tuning against local sand |
| High | 60,000 – 250,000 mPa·s | Anti-sag adhesives, thick putty, high-suction substrates, machine-applied plaster | Maximum retention and yield stress | Harder mixing, more air entrainment, slower wet-out |
Higher viscosity is not automatically better: it raises water demand and can make the mix short. Stay inside the band for your application.
How the number is obtained, and why that matters when comparing suppliers
HPMC viscosity is a relative measurement, not an absolute physical constant. Two data sheets quoting “20,000 mPa·s” can differ by a factor of two if the spindle, rotational speed, concentration or temperature differ. The industry convention is a 2% aqueous solution at 20 °C on a Brookfield viscometer, and even then the spindle and speed must be declared — LV with a small spindle at low speed reads higher than a larger spindle at higher speed on the same sample. Pharmacopoeial monographs take a different route and use a capillary method, so those figures are not interchangeable with Brookfield figures either.
When a supplier quotes a viscosity, ask three things: the concentration, the temperature, and the instrument with spindle and speed. If any of the three is missing, the number cannot be compared with anything.
Grade selection
Choosing the band before the grade
Viscosity is the selection axis. The three bands above cover what HPMC does in a mortar; the band that suits your system is set by the application and by your sand and binder, not by the highest number you can buy. Tell us the application and we will quote the band and the grade code together.
Applications
Which viscosity band fits which application
Dosages below are typical industry ranges for cement- and gypsum-based systems. They are starting points for a trial, not fixed recommendations: local sand grading, cement type, water demand and climate all move the optimum, and re-tuning is normal when a producer changes raw material source.
| Application | Why HPMC fits | Typical dosage, % of binder | Viscosity band | Reference method |
|---|---|---|---|---|
| Tile Adhesive | HPMC holds the mixing water against the suction of the tile and the substrate, so the adhesive stays workable long enough to wet a tile after trowelling; it also raises the yield stress that keeps a ribbed bed from slumping on a vertical face. | 0.25 – 0.45 | Medium | EN 12004; EN 1346; EN 1348 |
| Wall Putty | It keeps the paste open and trowellable while the filler and the wall draw water away, and the yield stress it builds stops a thick coat from sagging as it cures. | 0.30 – 0.60 | Medium – high | — |
| Gypsum Plaster | It retains water in a mix that would otherwise stiffen as the substrate draws suction, and keeps the paste lubricated so it spreads without lumping; setting time is left to a dedicated retarder, not to the ether. | 0.05 – 0.30 | Low – medium | EN 13279; ASTM C472 |
| Waterproof Mortar | It keeps the mix workable at the low water-to-binder ratio these systems need, so the mortar wets out and closes pores instead of tearing under the trowel, and the film it leaves holds adhesion on damp substrates. | 0.20 – 0.40 | Medium – high | EN 14891 (system) |
| Self-leveling | It sets the yield stress so the compound both flows and self-levels while still resisting segregation and bleeding — the balance a floor compound depends on. | 0.02 – 0.10 | Low | EN 13813 |
| Masonry Mortar | It holds water against the suction of brick and block and keeps the mortar workable in the tub, so the bond develops evenly instead of the mix stiffening before it is placed. | 0.02 – 0.10 | Low – medium | EN 1015-8 |
| Water-based Paint | It thickens the aqueous phase, suspends pigment and sets the rheology profile of the paint, which is what governs levelling, spatter and freeze-thaw stability in the can. | 0.2 – 0.6 | Low | — |
| EIFS / ETICS | It retains water in the adhesive and base coat while the insulation board and substrate pull it away, and it keeps the paste open long enough to embed the reinforcing mesh without re-wetting. | Available on request | Available on request | — |
Dosage is a starting point, not a specification — confirm it on a trial with your own sand, cement and mixing water. Grade-specific values are released with the TDS.
Two rows deserve a warning. In self-levelling compounds the working window is narrow enough that a 0.02% error changes flow visibly, so pre-blend a master batch rather than dosing at the mixer. In gypsum systems, HPMC controls water retention but does nothing for setting time — that needs a dedicated retarder, and adding more HPMC to slow the set is a common and expensive mistake.
Comparison
HPMC against the alternatives
Read across for the property that limits your formula, and read the last column first: it is where each additive stops being the right choice.
| Additive | Ionic | Water retention | Enzyme resistance | Typical role | Where it falls short |
|---|---|---|---|---|---|
| HPMC (this product) | Non-ionic | High | Good | Broad-purpose retention and rheology in cement and gypsum | Entrains air at high dosage; gels when heated |
| MHEC | Non-ionic | Very high per unit dose | Good | Tile adhesive and gypsum systems in some markets | Higher cost per kg; different shear response, so a straight swap needs a trial |
| HEC | Non-ionic | Medium – high | Good | Paints and coatings | Poor delayed solubility; less common in dry-mix mortar |
| CMC | Anionic | Medium | Good | Detergents, drilling fluids, some putty formulas | Reacts with calcium in cement systems, so retention falls and the mix can thicken unpredictably |
| Starch ether | Non-ionic | Low on its own | Lower | Workability, sag resistance, surface finish | Always blended with a cellulose ether; can reduce strength at high dosage |
| Redispersible polymer powder | Not a cellulose ether | None | — | Adhesion, flexibility, tensile strength after curing | Does not retain water; complementary to HPMC, not a substitute |
Relative comparison for orientation only; the ranking changes with dosage and with the local sand and cement.
Where HPMC is the wrong choice
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It does not replace redispersible polymer powder
HPMC gives water retention and rheology; it does not deliver tensile adhesion after heat ageing or the flexibility that EN 12004 C2 tests are looking for.
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It is not a retarder
Setting time is controlled by a dedicated retarder, and over-dosing HPMC to slow the set trades a rheology problem for a strength problem.
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It does not waterproof
Lowering water absorption needs a hydrophobic additive or a water-repellent powder; HPMC only changes how water moves while the mix is fresh.
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Above roughly 0.6% of binder in a cement system
the air it entrains starts to cost compressive strength faster than the extra retention is worth.
Supply
Packaging, storage and compliance
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Packaging
25 kg multi-layer paper bag with a polyethylene liner; 500 kg and 1000 kg jumbo bags. Custom-printed packaging is available on request.
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Storage
Keep sealed and dry, below about 30 °C, away from direct sunlight and away from odours. The powder is hygroscopic: moisture taken up in storage forms lumps that do not redisperse properly, and a bag that has been open for weeks behaves differently from a fresh one. Under these conditions the usual shelf life is 12 months in the unopened original packaging.
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Compliance and documents
Cellulose ethers are generally not classified as dangerous goods for transport, but the classification that applies is the one in the SDS for the specific grade — check it rather than assuming. A TDS, an SDS and a batch COA accompany every shipment, and a Certificate of Origin is issued with the export documents; the COA is the one that matters when a batch has to be released against a specification. The dust is a nuisance rather than a hazard in normal use, so local exhaust ventilation and a dust mask are the standard controls where bags are opened and emptied.
Downloads
Datasheets for the whole HPMC range.
FAQ
Frequently asked questions
What does HPMC do in tile adhesive?
It retains mixing water, extends open time and provides anti-sag. The usual starting point is 0.25–0.45% of binder for C1 and C2 adhesives, rising towards 0.50% where the T classification in EN 12004 applies and slip has to stay at or below 0.5 mm. Dosage is then re-tuned against the actual sand, cement and site temperature.
Which HPMC viscosity should I use for wall putty?
The medium to high band, roughly 40,000–100,000 mPa·s at 2% and 20 °C, is the common starting point, and high-suction substrates or thick coats push towards the upper end. Higher is not automatically better: an over-thick putty traps air, dries unevenly and sands poorly, which is why the band is chosen with the filler and water demand.
How much HPMC is used per tonne of mortar?
For tile adhesive, 0.25–0.45% of binder works out at 2.5–4.5 kg per tonne of binder. For gypsum plaster the usual window is 0.5–3 kg per tonne. Both figures are industry starting points; the correct value comes from a trial with the actual sand, cement and mixing water, because retention depends on what the substrate and the aggregate take out of the mix.
Why does HPMC form lumps when mixed with water?
Standard HPMC swells the moment it meets water, so the outer layer of each particle gels and seals the dry core inside. Use a delayed-solubility grade, dry-blend the powder with the other solids before adding water, and add water under shear. Lumps formed this way do not dissolve later; they show up in the finished surface as hard specks.
What is the difference between HPMC and MHEC?
Both are non-ionic cellulose ethers used for water retention in construction. MHEC generally delivers more water retention per unit dose in cement systems and has the higher gelation temperature, while HPMC has the wider supply base. The real choice is made on trial performance and landed cost for a specific formula, not on the data sheet alone.
Is HPMC the same as hypromellose?
Yes. Hypromellose is the international nonproprietary name and the pharmacopoeial name for hydroxypropyl methyl cellulose; HPMC is the abbreviation used in construction. CAS 9004-65-3 covers the material class. Grades differ in substitution, viscosity and purity, so a pharmaceutical grade is not a drop-in substitute for a construction grade even though the chemical name matches.
Applications
Where this product is used
Wall Putty
Smooth trowelling, crack resistance and open time for skim coats.
Coming soon
Gypsum Plaster
Controls setting time and water demand in machine-applied plasters.
Coming soon
Waterproof Mortar
Dense film formation and adhesion on wet substrates.
Coming soon
Get the TDS and a sample
Send the application, the binder system and the viscosity band you are working with, and you get back the matching TDS plus a 200 g sample for a plant trial. Technical questions are answered by the application team, not by a sales script. Reply within 12 working hours.